| With the rapid development of the rail transit industry,the running speed of vehicles has been continuously increased.The operating environment of different types of vehicles is complex and changeable,which makes the load on the vehicle structure randomly vary.The possibility of fatigue failure is increasing,which seriously affects the driving safety.In engineering practice,the structural strength of vehicles is checked mainly through static fatigue methods,while the influence of structural vibration characteristics is ignored.Therefore,it is very important to carry out the research on the fatigue life of structural parts of rail vehicle by the vibration fatigue life assessment method.In this thesis,taking the rail vehicle as the application background,the car body that is the large load-bearing structure of the vehicle and the antenna beam that is the vibration structure suspended at the end of the bogie as the carrier,the typical fault cases in the service of the vehicle as the boundary,the random vibration fatigue life prediction is deeply studied.The main works are as follows:1)A rigid-flexible coupled dynamics model and a longitudinal dynamics model of the high-speed train considering the car body as the flexible body are established.The model is verified by the measured vibration acceleration and frequency response of the car body.The running attitude of the vehicle is studied,and a method to invert the low-frequency load spectrum of the car body based on the measured acceleration of the bolster is proposed.Based on the mount dynamic stiffness method and load calibration,an inversion method for the measured car body load spectrum is proposed.2)Based on the theory of quasi-static superposition method and modal superposition method in dynamic stress simulation calculation,the load frequency domain separation method of EMU body is proposed.The car body load is divided into low frequency and high frequency parts by the critical frequency,and the critical frequency is half of the first-order elastic modal frequency of the structure.A vibration fatigue dynamic stress simulation method suitable for inertial structures is presented.3)A finite element model of the aluminum alloy EMU is established.The accuracy of the model is verified by tests.Based on the fatigue assessment process of non-welded and welded structures in EN17149,the effects of straight lines,curves of different radius,turnouts,and start/brake conditions on the life of the car body structure are studied through dynamic simulation.After inversion of the low-frequency load spectrum of the car body based on the measured load spectrum of car body,the effects of vehicle entry and exit,high-speed operation,and start/brake on the life of the car body structure are evaluated.The fatigue life of the care body structure is evaluated based on the high-frequency load,and the mechanism of the structure’s resonance caused by the high-frequency vibration of the structure is identified,and the suggestion for the structural life evaluation is given.4)The research on the local cracking problem of the antenna beam of the suspension structure at the end of the bogie is carried out.The modal parameters of the antenna beam are identified through simulation and actual measurement.Based on the IEC61373 ASD spectrum and the measured vibration spectrum,the uniaxial and multi-axis random vibration fatigue life of the antenna beam is evaluated.Combined with the time-domain and frequency-domain characteristics of the measured dynamic stress and acceleration signal of antenna beam,the mechanism that causes the antenna beam modal resonance and finally leads to the structural damage is identified.5)An optimization strategy of the antenna beam structure is proposed,and the life of the improved antenna beam structure is verified by simulation and experiment to meet the standard and practical requirements.Based on the load spectrum of the antenna beam fault diagnosis test,the vibration transmission law from the axle box body-the end of the frame-the mounting seat of the antenna beam-the middle of the antenna beam is studied,and the reasons for the failure of the antenna beam structure are identified,which provides data support for subsequent structural optimization and verification tests. |
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